Add $(uniq token...) native function to Make

This reduces mono repo `make` latency from 336ms to 226ms.

third_party/make/README.cosmo

@@ -16,7 +16,10 @@ LICENSE
 LOCAL CHANGES
 
   - Introduce $(uniq token...) native function
-  - .INTERNET variable to allow internet access
+  - Remove code that forces slow path if not using /bin/sh
+
+TODO
+
   - .PLEDGE variable which restricts system calls
   - .UNVEIL variable which controls Landlock LSM
   - .STRICT variable to disable implicit unveiling
@@ -28,5 +31,3 @@ LOCAL CHANGES
   - .NPROC variable which tunes fork() / clone() limit
   - .NOFILE variable which tunes file descriptor limit
   - .MAXCORE variable to set upper limit on core dumps
-  - Do automatic setup and teardown of TMPDIR per rule
-  - Remove code that forces slow path if not using /bin/sh

third_party/make/function.c

@@ -21,6 +21,8 @@ this program.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "job.h"
 #include "os.h"
 #include "commands.h"
+#include "libc/mem/critbit0.h"
+#include "libc/log/rop.internal.h"
 #include "debug.h"
 
 
@@ -1366,6 +1368,45 @@ func_intcmp (char *o, char **argv, const char *funcname UNUSED)
   return o;
 }
 
+/*
+  chop argv[0] into words, and remove duplicates.
+ */
+static char *
+func_uniq (char *o, char **argv, const char *funcname UNUSED)
+{
+  char *p;
+  size_t len;
+  int mutated;
+  bool once = false;
+  const char *s = argv[0];
+  struct critbit0 t = {0};
+
+  while ((p = find_next_token (&s, &len)))
+    {
+      ++s;
+      p[len] = 0;
+      RETURN_ON_ERROR ((mutated = critbit0_insert (&t, p)));
+      if (mutated)
+        {
+          if (once)
+            o = variable_buffer_output (o, " ", 1);
+          else
+            once = true;
+          o = variable_buffer_output (o, p, len);
+        }
+    }
+
+  critbit0_clear (&t);
+
+  return o;
+
+OnError:
+  critbit0_clear (&t);
+  OSS (error, NILF, "%s: function failed: %s",
+       "uniq", strerror (errno));
+  exit (1);
+}
+
 /*
   $(if condition,true-part[,false-part])
 
@@ -2522,6 +2563,7 @@ static struct function_table_entry function_table_init[] =
   FT_ENTRY ("value",         0,  1,  1,  func_value),
   FT_ENTRY ("eval",          0,  1,  1,  func_eval),
   FT_ENTRY ("file",          1,  2,  1,  func_file),
+  FT_ENTRY ("uniq",          0,  1,  1,  func_uniq),
 #ifdef EXPERIMENTAL
   FT_ENTRY ("eq",            2,  2,  1,  func_eq),
   FT_ENTRY ("not",           0,  1,  1,  func_not),